Sangoma Netborder SS7, User Manual

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8
Megaco/H.248 Media Gateway Configuration
8.1 Overview
H.248 or Megaco or Gateway Control Protocol is a recommendation from ITU which defines protocols
that are used between elements of a physically decomposed multimedia gateway. It is an
implementation of the Media Gateway Control Protocol Architecture (RFC 2805). H.248 is also called
Megaco or in IETF domain. It is now known as Gateway Control Protocol.
H.248/Megaco is standard protocol for controlling the elements of a physically decomposed
multimedia gateway, which enables separation of call control from media conversion. H.248/Megaco
is a master/slave protocol used to separate the call control logic from the media processing logic in a
gateway.
The H.248/Megaco model describes a connection model that contains the logical entities, or objects,
within the Media Gateways (MGs) that can be controlled by the Media Gateway Controller. The main
entities are Contexts and Terminations.
8.1.1 Terminations
These source or sink one or more media streams or control streams. Terminations may be
physical or ephemeral.
Physical Terminations represent physical entities that have a semi-permanent existence. For
example, a Termination representing ports on the gateway, such as TDM channel or DS0
might exist for as long as it is provisioned in the gateway. Ephemeral Terminations represent
Connections or data flows, such as RTP streams, or MP3 streams, and usually exist only for
the duration of their use in a particular Context.
Terminations have properties, such as the maximum size of a jitter buffer, which can be
inspected and modified by the MGC. A termination is given a name, or Termination ID, by the
MG.
8.1.2 Contexts
These are star connections created by associating multiple terminations. A Context is a logical
entity on an MG that is an association between a collection of Terminations. A NULL context
contains all non-associated terminations. A Context is a logical entity on an MG that is an
association between a collection of Terminations. A ContextID identifies a Context.